1. Field of the Invention
The invention relates generally to a wheel hub drive and more particularly to a wheel hub drive having a drive motor and a single or a multi-stage planetary gear train which includes an input-end sun wheel directly or indirectly connected to the output shaft of the drive motor and an output element directly or indirectly connected to the wheel hub. A releasable connecting arrangement is located at the end of the drive motor output shaft remote from the drive motor for connecting and disconnecting components of the wheel hub drive. A hydraulically and spring-actuated axially movable piston operates the connecting arrangement.
2. Description of Related Prior Art
This type of wheel hub drive is disclosed in U.S. Pat. No. 4,213,514 entitled "Hydraulic Wheel Drive with Clutch" wherein a connecting multi-plate clutch is operated by a hydraulically operated annular piston which acts directly on the clutch disks and is located in the immediate area of the clutch disks. In the arrangement disclosed in the patent, the clutch requires a substantial amount of space because of the location of the piston. Additionally, it is necessary to pass the hydraulic fluid to operate the clutch through the entire length of the wheel hub drive which includes the drive motor, the planetary gear train and the clutch. An annular piston is supported by a bearing located in a reinforced center cover which can be removed to service the clutch. The output shaft of the drive motor extends through the clutch. This arrangement is expensive from both the production and the engineering standpoints.